*2.4.3.1.4 Sublethal effects of acaricides on prey consumption of treated female and the subsequent generation*

For assessment of any sublethal effect on prey consumption of treated predators 20 to 30 only protonymphal stage (to decrease the adverse effect of prey webbing on predator) of *T. urticae* were placed on each treated and untreated (control) leaf disc as predator food source. Forty-eight hours after treatment, an unexposed male from the rearing arena was presented to each surviving female. Males that died during the experiments were replaced. The prey consumption of *P. plumifer* females was recorded separately for their pre-oviposition, oviposition and postoviposition periods, because of the different rates for each one, were observed previously in our experiments [39]. Fresh preys were replaced with consumed ones in treated and untreated arena every 24 hours to maintain a constant daily food supply. Through the experiment adult male and female *P. plumifer* were kept pair. Consumption by the male measured previously as two protonymph per day, which subtracted from the total.

The eggs laid by the treated and untreated females were collected daily and moved to untreated leaf disc for assessment of sublethal effect on prey consumption of *P. plumifer* treated female's offspring from nymph to dead of the last female. Depending on the number of eggs, that laid by exposed females, approximately 10 and 30 replications were carried out for abamectin and fenpyroximate treatments, respectively. After emergence of the adults, males and females were paired and male consumption was subtracted as described previously. Individuals were checked daily and the number of protonymphs of *T. urticae* that had been consumed were counted, recorded and replaced with fresh ones until the death of the last predator. 10, 20, 30 and 20 protonymph stage of *T. urticae* were provided daily for proto- and deutonymphal stages and the pre-oviposition, oviposition and post-oviposition periods of predators, respectively. This was in excess of that required for daily consumption, as observed by our earlier experiments [39].

#### *2.4.3.1.5 Data analysis*

Mortality was corrected by using Abbott's Equation [41]. The LC50, other sublethal concentrations and the regression equation were evaluated for the dose mortality line were extracted by using a probit program of SAS. The 95% confidence intervals of LC50 obtained from 72 h acute concentration–response curves developed from the responses of adult females and males, for comparing susceptibility of them. Any deviation from the expected sex ratio of 1:1 was determined using a chi-square analysis. For comparing longevity, fecundity, and duration of each stage among different concentrations and the control, analysis of variance (ANOVA) was used. Least Significant Difference (LSD) sequential test was used for comparing the means.

Based on the procedures developed by some authors [33, 42], the following life-table parameters were calculated: gross reproductive rate (*GRR*), net reproductive rate (*R*0), intrinsic rate of increase (*r*m), finite rate of increase (*k*), doubling time (*D*), mean generation time (*T*), intrinsic rate of birth (*b*) and intrinsic rate of death (*d*). Jackknife method was used to generate and compare mean demographic parameter estimates with SE values [43]. For comparing life table parameters among different concentrations and controls analysis of variance (ANOVA) was used. The means were compared using LSD sequential test.

### *2.4.3.2 Results*

Our results of several experiments on side effects of acaricides on predatory mite *P. plumifer* demonstrated that, to evaluate the total effects of acaricides, in spite of effects on treated predator, assessment of all effects on offspring from treated females (subsequent generation) is necessary. Otherwise the real effects of residual exposure on performance of predatory mites would have incomplete end points. Our study proved that abamectin and fenpyroximate had an adverse effect on biological performance of *P. plumifer* females and their offspring [34, 39, 40]. Many other studies showed these effects on phytoseiid mites too [38, 44–47].

#### *2.4.3.2.1 Sublethal effects of acaricides on mortality*

Reduction in settlement ratio of phytoseiid mites treated by abamectin reported in our study and several other studies too [34, 36, 44]. Our results along with other studies on predators of *T. urticae* showed that most mortality occurred in 3 days after exposure to abamectin while in the first day there was no effect or a few effects [36, 48–50]. Abamectin was too toxic for *P. plumifer* in our study; it caused 100% mortality in female predators in 0.1 concentration that recommended for *T. urticae* control in the field. Moreover *P. plumifer* males were more susceptible than females to abamectin and fenpyroximate residue.

### *2.4.3.2.2 Sublethal effects of acaricides on eggs hatch and sex ratio of subsequent generation*

The eggs laid by treated females were hatched at least 96.08% in fenpyroximate treatment so this parameter was not affected significantly. The sex ratio of *P. plumifer* was affected by fenpyroximate and the treatment caused a reverse in sex ratio. Sex ratio was 16:8 (female:male) in subsequent generation of untreated females that changed to 10:26 (female:male) in subsequent generation of treated females with LC30 of fenpyroximate. Increasing the number of male in comparison with female

#### *Biological Control of Tetranychidae by Considering the Effect of Insecticides DOI: http://dx.doi.org/10.5772/intechopen.100296*

in subsequent generation of treated female with fenpyroximate can be the other reason of decreasing the predator population after two generations [36, 39]. The sex ratio and egg hatch rate of *P. plumifer* were not significantly affected by abamectin sublethal concentrations.
